This invention relates generally to methods and systems for controlling work machines and, more particularly, to methods and systems for controlling the steady-state speed of hydraulic cylinders associated with the work machines.
A variety of work machines are utilized for construction and excavation work. Examples of such machines include excavators, wheel loaders, front shovels and front end loaders. Each one of these types of machines includes a work implement so that a variety of tasks can be performed. The work implement is supported by a plurality of linkages coupled to hydraulic cylinders.
The machine operator typically uses a plurality of levers to manipulate the work implement and supporting linkages into a variety of positions at different speeds to perform the various tasks that are required on a typical earth moving job. Each cylinder is typically controlled at a steady-state rate for-a given lever position according to a predetermined relationship. This relationship is encoded in a non-volatile memory, such as, but not limited to, Read Only Memory (xe2x80x9cROMxe2x80x9d), in a table format. The table is typically large to accommodate the desired steady-state speed of each of the cylinders for a plurality of lever positions. Also, since this table is programmed into ROM or otherwise incorporated in a non-volatile memory, it is inflexible.
Thus, there is a need for efficient use of memory in defining the desired relationship between steady-state speed of a cylinder and lever position and for flexibility in defining the desired relationship.
The present invention is directed to overcome one or more of the problems as set forth above.
In one aspect of this invention, a method is provided for controlling the steady-state speed of a cylinder in an electrohydraulic system having multiple cylinders and multiple levers for controlling each of the cylinders. The method includes storing a limited number of parameters defining at least one desired relationship between steady-state speed and lever position for each cylinder, determining a current desired relationship for each of the cylinders from the associated at least one desired relationship, determining a current position of one of the levers associated with one of the cylinders, and controlling the steady-state speed of one of the cylinders based on the limited number of parameters defining the current desired relationship and the position of the lever.
In another aspect of the invention, a system is also provided for carrying out the steps of the above described method. The system includes a plurality of levers for controlling each of the cylinders in the electrohydraulic system. The system also includes a controller in communication with the levers and the cylinders for storing a limited number of parameters defining at least one desired relationship between steady-state speed and lever position for each cylinder, determining a current desired relationship for each of the cylinders from the associated at least one relationship, determining a current position of one of the levers associated with one of the cylinders, and controlling the steady-state speed of one of the cylinders based on the limited number of parameters defining the current desired relationship and the position of the lever.